1. Field of the Invention
This invention relates to a novel liquid crystal substance and a liquid crystal composition containing the liquid crystal substance, and more particularly it relates to a chiral liquid crystal substance having an optically active group and a chiral liquid crystal composition containing the same.
2. Description of the Related Art
At present, as liquid crystal display elements, the (Twisted Nematic) type display mode has been most broadly employed, but it is inferior to emissive type display elements such as those of electroluminescence, plasma display, etc. in the aspect of response speed. Thus, various improvements in this respect have been attempted, but nevertheless it does not seem that a possibility of improvement to a large exent has been achieved. Accordingly, various liquid crystal display devices based upon another principle in place of that of the TN type display elements have been attempted. As one of these devices, there is a device according to a display mode utilizing ferroelectric liquid crystals (N. A. Clark et al, Applied Phys. lett., 36,899 (1980)).
This mode utilizes the chiral smectic C phase (hereinafter abbreviated to SC* phase) or chiral smectic H phase (hereinafter abbreviated to SH* phase), and the temperature range exhibiting these phases is preferred to be in the vicinity of room temperature.
Mainly in order to develop liquid crystal substances suitable for being utilized for this display mode, the present inventors have searched for various liquid crystal substances having an optically active group and as a result have achieved the present invention.